Capacity pickup follow-up system



Dec. 19, 1950 w. K. ERGEN 2,534,505

CAPACITY PICKUP FOLLOW-UP SYSTEM Filed Dec. 15, 1944 INVENTOI? WILL/17M /I. E/TGEN Patented Dec. 19, 950

,UNlTED sm'rss mam-150m William K. Ergen, Minneapolis, Minn, assignor to Minneapolis-Honeywell Regulator Company, -lliinnealmlis, Minn a corporation of Delaware Application December 15, 1944, Serial No. 568,333

I imperfections on a new and improved telemetric ing my improved pick-up.

5 Claims. (Cl. 318-25) This invention relates to the field of electrical engineering, and more specifically to the field of motor control systems and that I of telemetric systems for making available at a remote point an indication of change in a condition, or for .performing at a first point a control function initiated at a second relatively remote point. It is an object of my invention to provide a new and improved motor control system for use with reversible electric motors.

It is an object ofmy invention to provide a new and improved self-balancing electrical network. It is an object of my invention to provide a new and improved capacity pick-up especially constructed to minimize the eilect of manufacturing the accuracy of the complete device.

It is another object of my inventionto provide system embody- It is yet another. object of my invention to provide a new' and improved condition control system in which a motor is controlled, according to my improved motor control system, by variation in my improved capacity pick-up.

It is a further object of my invention to provide a new and improved capacity pick-up employing' a dielectric vane rotatable between plates of electrically conductive material, so that the electric field between the plates is not appreciably distorted by inaccurate mounting of the movable vane, or by movement of the vane toward or away from the plates;

4 Various other objects, advantages, and features of novelty which characterize my invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages and obects attained by its use, reference should be had to the subjoined drawing, which forms a further part hereof, and to the accompanying descriptive matter, in which I have illustrated and described a preferred embodiment of my invention.

In the drawing: 45 s Figure 1 is a plan view, partly in section, of my form a second fixed capacitor 34, while plate II 7 improved capacity pick-u and plate It and plate II and plate I6, respec- Figure 2 is a sectional elevation of my pick-up, taken along the line 2-2 of Figure 1, and

' Figure 3 is a schematic diagram showing the general association of the parts making up my improved motor control and telemetric system, and em ying my improved capacity pick-up.

Referring first to Flguresl and 2, it be seen that my improved capacity pick-up is identified b the reference numeral I0, and comprises afirst circular metallic plate I I suitably insulated from ground and other electrical conductors by a nonconducting member I2, which may be of any desired nature. Plate II is to compriseone electrode of each of a plurality of capacitors, and to that end the plate is provided with a terminal Is for making electrical connection therewith.

Supported in equally spaced parallel relationship irom plate I I area plurality of plates I4, I5, I6, and ll of equal area and similar outline. I have shown the plates as supported on insulating pillars 20, but any equivalent supporting means such as may occur to those skilled in the mechanical arts may be used. Upper plates I4, 15,16, and I! are designed to cooperate with plate I [to comprise a group of capacitors of equal normal capacitance, there being'an air dielectric between the plates, and the plates are respectively provided with terminals 2 I, 22, 23, and 24. I

Plate II provides atits center a foot bearing 29 for a shaft 25 carrying an actuating arm'28. The shaft may in practice be provided with an outboard bearing and such other conventional refinements of mechanical structure as may be desired: these are not illustrated in the schematic showing of Figure 2.

Fixed to shaft 25 for integral rotation therewith is a vane 21 of a solid dielectric material of uniform thickness and of an outline similar to that of the upper plates. It will be seen that to the extent to which vane 21 intervenes between plate II and one of the upper plates, IS, IS, or II, the average dielectric constant of the material between the plates of that particular capacitor is altered. Each of the four-capacitors may therefore be considered as a variable capacitor whenever vane 21 moves within its electrostatic field, and as a fixed capacitor at all other times. This is shown schematically in Figure 3, which illustrates an arrangement of capacitors equivalent to that shown in Figure 1, where vane 24 is shown as extending equally under plates I5 and I6. Plate I I and plate I combine to form a first fixed capacitor II and plate II and plate Il combine to I I and I! would be a variablecapacitor.

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Arm has been shown as being provided with an aperture 31 for connection to a suitable opcrating link. This link is identified by the reference numeral 88 in Figure 8, and is shown as being operated by a pressure responsive bellows ll. It will be appreciated, however, that this arm may be arranged for operation by any desired condition responsive member, and that if it is desired to cause rotation of shaft 25 through a considerable angle, for example one or more complete revolutions, a gear and pinion or other suitable drive between shaft II and the condition responsive member can be substituted for arm and link 35.

Referring again to Figure 3 of the drawing, it will be seen that,my complete circuit includes a voltage distributor, 38 comprising endless resistance member 40 cooperating with a contact resistor, and mi; be disregarded. The following outline of operation is based on the assumption that the pick-up currents can be neglected.

arm ll, an amplifier 42, a split phase motor 43,

and a transformer I having a primary winding ll and a secondary winding ll, the latter being provided with a center tap l1. Electrical energy is provided to amplifier l2 and primary winding ll of transformer 44 by conductors Ill and Ii from any suitable source of alternating current.

Endless resistance member 40 is shown to comprise a plurality of resistors 52, 53, t4, and 58 connected in a closed series circuit, so that there is a common terminal 56 between resistors 52 and 53, a common terminal between resistors N and I4, a common terminal II between resistors II and BI, and a common terminal I! between resistors 58 and II. The resistances of resistors 52, lit, BI, and II are equal and uniformly distributed.

be-understood that motor 43 includes a suitable high ratio gear reducer to adapt it for use in this location. Shaft It is also connected to actuate a control device which may be an indicator, a heat flow control member such as a damper, or any other desired apparatus.

Motor 48 is shown as energized from amplifier 42 through conductors ll so that it reverses in direction with reversal in phase of the signal applied to the input of the amplifier. This general method 01' motor control is disclosed in Anschuts-Kaempfe Patent 1,586,233, but it must be clearly understood that my invention will operate with perfect satisfaction with any other type of amplifier in which the output of the amplifier is dependent in phase upon the phase of the input voltage.

Operation conventional input resistor (not shown) of amplifier 42; Center tap I1 is grounded as at 11.

The impedances of capacitors ll, 32, 83, and M are ordinarily high compared with the resistances of members 82, 6!, II, and It. Therefore, the currents required to producesignifieant 12 drops across the capacitors are very small com- 75 pared to the currents flowing around the circular As previously pointed out, vane 21 and plates ,ll, ll, and ii are similar in shape and equal in area, and in practice the spaces between the radially adjacent edges of the plates are extremely small. With air only as the common dielectric 0f the capacitors; that is, in the absence of vane 21, the capacitors are of equal capacitance: let the magnitude of this capacitance be represented by C. The intromission of a portion of vane 21 between the plates comprising any capacitor can only increase this capacitance, since the dielectric constant of the material of which the vane is made is many times that of air. 0 is therefore the minimum capacitance of each of the capacitors.

It is proper to represent each capacitor as a fixed capacitor of the minimum capacitance C connected in parallel with a variable capacitor C1 of capacitance varying from zero to a maximum value Car. The magnitude of Cm is the difference between the minimum capacitance and the capacitance when the vane is completely interposed between the plates of a given capacitor it From the geometry of the device, the variable capacitors are of equal maximum capacitance, and the capacitance change islinear with angular displacement of the vane up to in either direction from the position of maximum capacitance for a given capacitor. The remaining movement of the vane has no effect on the capacitance of the capacitor in question. The variable capacitance of capacitors Ii, 82, II, and N are identified below by the numerals C1, C2, C3, and C4.

In the position of the vane disclosed in Figure l, capacitors II and :4 have the minimum value: that is, 01 and C4 have the value zero. The who is shown in a midposition between plates II and II: the capacitances of capacitor Cs and C: are therefore equal and have half of their maximum magnitude.

Let the voltage output of winding is be of magnitude 21!:this is the potential difference between sliders I and 82. Current fiows from slider ll ins. pair of paths, the first including portion 18 of resistor 52, resistor It, and portion 1| of resistor I4, and the second including portion 14 of resistor 52, resistor II, and portion ll of resistor ll. Since the resistances of these two paths are equal, the currents are also equal: let the magnitude of each of these currents have the value I.

In Figure 3, the angle a may be defined as the counterclockwise displacement of slider 8| from terminal ll. Let the resistance of each of the resistors have a value R, and let K represent the resistance of portion 14 of resistor 52 (and of portion 1 of resistor ll). Then K:R: :az90

- C: and Ca.

' 8 and thelvoltage roplacross portions 10 and 10 of resistors]! and N have the value 1K. The potentials of points I, II, It, and II, with respect to center tap 41 of winding 48, may be defined as follows:

. The potential diflerences between certain terminals can now be determined: that between terminals II and II is identified by V1, that between terminals I1 and 59 by V2, and that between terminals I and I! by Vs. The voltage is considered positive when themfjlrst numbered terminal is positive for a positive condition of slider ll.

- system by sliders GI s,ss4,sos

vane 21 so'that c1 isno loamequal to es." s

newratio I now exists, Equation 10 is no longer met and a newsignal is impressed on the amplifier, causing actuation of device 30 and rebalancing' of the and as just described. that when the'ratio It will be realized exceeds the ratio IK-E E-IR+IK a signal of one phase is impressed upon the input of amplifier 42, while when the'signal impressed upon the input of the ampli her is of the opposite phase, thus bringing about the reversal in the operation of motor 43 referred to above.

An important advantage of my invention over the conventional type of variable condenser in which the movable vane is of electrically con-' ductive material lies in the fact that the vane equal capacitors having capacitance C: the eii'ect of C; will be separately considered below. The circuit 5 9, OI, II, C, it, C, 23, 88, 51, is also symmetrical, and point I 3 remains at the same potential as center tap ll.

Terminal 22 is at potential EIR+IK and terminal 23 is at potential IK-E, both with respect to tap 41, and to the terminals are connected the ends of a voltage divider comprising capacitors For the point of junction of these two capacitors to be at the same potential as point ll, that is, as center tap 41, the impedances' of the capacitors must be proportional to the voltages impressed upon them: that is,

The .capacitances of the In the position of the pickup unit shown in Figures 1 and 3, C'z=Ca, and therefore the above condition is not met. A voltage difference accordingly exists'between point l3 and tap and a signal is consequently impressed upon the input of amplifier 42. Motor 43 is energized to rotate arm ll, altering the ration between R and K. The rotation is arranged to be in a direction which changes the ratio so as to fulfill the above condition, and when it is fulfilled the signal disappears from the amplifier and the motor stops. In this case when a clockwise direction and stops when K=R/2. The operation of the motor has meanwhile accomplished the desired control function through control device 30.

Suppose .now the pressure changes, moving ci=cs, the motor rotates in vidual terminals of need not be accurately parallel with the plates of the condenser. As shown in Figure 2, my vane 21 is perceptibly at an angle with respect to the plates comprising the condenser. If vane 21 were ofmetal there would be a concentration of the electrostatic field at the upper left hand corner and lower right hand corner of the vane section as shown in that figure, the field would be distorted and the response of the condenser to rotation of, arm 28 as a variation in the signal impressed upon the amplifier, which would result in operation of motor 43 in response to spurious signals. By provision of a dielectric vane instead of the electrically conducting vane, I hav avoided these disadvantages and have provided a greatl improved pickup unit which is sensitive, accurate, and free from errors such as those I have recited. Numerous objects and advantages of my-invention have been set forth in the foregoing description together with details of structure and function of the invention, and the novel features thereof are pointed out in the appended claims.

v The disclosure, however, is illustrative only, and

I may make changes in detail, especially in mat ter of shape, size and arrangement of parts, within the principle of the invention, to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. I

I claim as my invention:

1. In a device of the class described, a plurality of capacitors having a common terminal and individual terminals, ,a like plurality of resistors, means connecting said resistors in series to provide an endless resistance member, each terminal of each resistor being common with a terminal of another resistor, means connecting said common terminals of said resistors with said indisaid. capacitors, a Pair of would be distorted. Moreover, any play in the bearing of shaft 25 would appear a,ssa, sos

- spaced sliding contacts cooperating with said resistors, saidcontacts being arranged to:- movement in such fashion that the resistances between said contacts in opposite directions around said resistance member remain equal, center tapped means energizing said contacts from a source oi alternating voltage, electric motor plurality of impedance units, means connecting said units in series to provide an endless impedance member. each terminal of each unit being common with a terminal one other unit, means connecting said common terminals of said units with said individual electrodes of said capacitors, means supplying a pair of alternating voltages of opposite phase between a common supply terminal and two separate supply terminals, means connecting points on said endless impedance member to said separate supply terminals, a controlled device, and means energizing said device in accordance with the voltage between said common supply terminal and said common electrode oi said capacitor.

3. In a device of the class described, in combination, a plurality of capacitors having a common electrode and individual electrodes, a like plurality of impedance units, means connecting said units in series to provide an endless impedance member, each terminal of each unit being common with a terminal oi! one other unit, means connecting said common terminals of said units with said individual electrodes of said capacitors, means supplying a pair 0! alternating voltages of opposite phase between a common supply terminal and two separate supply terminals, means applying to spaced points on said endless impedance member the voltage between said separate supply terminals, movable dielectric means differentially varying the capacitances of said capacitors, and motor means varying the points of application of said voltage in accordance with the voltase between said common supply terminal and said common electrode of said capacitor.

4. In a device of the class described, in combination, a plurality of capacitors having a common electrode and individual electrodes, a like.

plurality oi impedance units means connecting said units, in series to provide an endless impedance member, each terminal of each unit being common with a terminal of one other-unit, means connecting said common terminals of said units with said individual electrodes oi said capacitors, means supplying a pair of alternating voltages of 8 opposite phase between a common supply terminal and two separate supply terminals, means applying to spaced points on said endless impedance member the voltage between said separate supply terminals, a motor, means difler- .entially varying the ,capacitances of said capacitors in accordance with a condition, and means energizing said motor from said source in accordance with the voltage between said common supply terminal and said common electrode 0 said capacitor. 5. In a device oi the class described, in combination: a balanceable network comprising capacitance means, including several capacitors having a common electrode and individual electrodes and a dielectric member diflerentially var!- ing the capacitances oi said capacitors, resistance means, including a like number of resistors and means connecting said resistors in series relation to form an endless resistance member, and means connecting each point common to two of said resistors to the individual electrode oi one of said capacitors; a source of electrical energy; means adjustably energizing said resistance means from said source, at two spaced points, to determine the potential of each of said common points with respect to a selected potential, an electric motor; means connecting said motor to adjust said energizing means so as to vary the potentials of said common points, and hence the potentials of said individual electrodes, with respect to said selected potential; means mechanically responsive to a condition; means connecting said last named means in driving relation to said dielectric member, to unbalance said notwork by varying the capacitances of said capacitors and hence to vary the potential of said common electrode with respect to said selected potential, and means energizing said motor in accordance with the diflerence between the potential or said common electrode and said selected potential;

WILLIAM K. ERGEN.

REFERENCES crrEn The following references are of record in the.

file of this patent:

UNITED STATES PATENTS France Aug. 3, 1983 

